Selective modulation of the surface properties of K-feldspar and fluorapatite is the key to achieving efficient separation of the two. In this study, Decyldimethylammonium Chloride (DDAC) was used as a novel collector to achieve flotation separation of K-feldspar and fluorapatite. The results of flotation experiments showed that K-feldspar could be selectively floated when the concentration of DDAC was 10 mg/L at pH=3.0, and the recovery of K-feldspar reached 97.07%, while the recovery of fluorapatite was only 6.68%. Zeta potential test proved that the cationic collector DDAC could selectively increase the surface potential of K-feldspar, and the increase of K-feldspar potential at DDAC concentration of 30mg/L was 43.5 times that of fluorapatite. Infrared spectroscopy and XPS detection revealed that DDAC selectively reacted with oxygen sites on the surface of K-feldspar and adsorbed on the surface of K-feldspar through hydrogen bonding and electrostatic adsorption, but had no effect on fluorapatite.